Getting started with .NET on RHEL 7
Installing and running .NET Core 3.1 on RHEL 7
Abstract
Making open source more inclusive
Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.
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Chapter 1. Introducing .NET Core 3.1
.NET Core is a general-purpose development platform featuring automatic memory management and modern programming languages. Using .NET, you can build high-quality applications efficiently. .NET Core is available on Red Hat Enterprise Linux (RHEL) and OpenShift Container Platform through certified containers.
.NET Core offers the following features:
- The ability to follow a microservices-based approach, where some components are built with .NET and others with Java, but all can run on a common, supported platform on RHEL and OpenShift Container Platform.
- The capacity to more easily develop new .NET Core workloads on Microsoft Windows. You can deploy and run your applications on either RHEL or Windows Server.
- A heterogeneous data center, where the underlying infrastructure is capable of running .NET applications without having to rely solely on Windows Server.
.NET Core 3.1 is supported on RHEL 7, RHEL 8, RHEL 9, and OpenShift Container Platform versions 3.3 and later.
Chapter 2. Installing .NET Core 3.1
To install .NET Core on RHEL 7 you need to first enable the .NET Core software repositories and install the scl tool.
Prerequisites
Installed and registered RHEL 7 with attached subscriptions.
For more information, see Registering the System and Attaching Subscriptions.
Procedure
Enable the .NET Core software repositories:
$ sudo subscription-manager repos --enable=rhel-7-variant-dotnet-rpmsReplace variant with
server,workstationorhpc-nodedepending on what RHEL system you are running (RHEL 7 Server, RHEL 7 Workstation, or HPC Compute Node, respectively).Verify the list of subscriptions attached to your system:
$ sudo subscription-manager list --consumed
Install the
scltool:$ sudo yum install scl-utils -y
Install .NET Core 3.1 and all of its dependencies:
$ sudo yum install rh-dotnet31 -y
Enable the
rh-dotnet31Software Collection environment:$ scl enable rh-dotnet31 bash
You can now run
dotnetcommands in thisbashshell session.If you log out, use another shell, or open up a new terminal, the
dotnetcommand is no longer enabled.WarningRed Hat does not recommend permanently enabling
rh-dotnet31because it may affect other programs. For example,rh-dotnet31includes a version oflibcurlthat differs from the base RHEL version. This may lead to issues in programs that do not expect a different version oflibcurl. If you want to enablerh-dotnetpermanently, addsource scl_source enable rh-dotnet31to your~/.bashrcfile.
Verification steps
Verify the installation:
$ dotnet --info
The output returns the relevant information about the .NET Core installation and the environment.
Chapter 3. Creating an application using .NET Core 3.1
Learn how to create a C# hello-world application.
Procedure
Create a new Console application in a directory called
my-app:$ dotnet new console --output my-appThe output returns:
The template "Console Application" was created successfully. Processing post-creation actions... Running 'dotnet restore' on my-app/my-app.csproj... Determining projects to restore... Restored /home/username/my-app/my-app.csproj (in 67 ms). Restore succeeded.
A simple
Hello Worldconsole application is created from a template. The application is stored in the specifiedmy-appdirectory.
Verification steps
Run the project:
$ dotnet run --project my-appThe output returns:
Hello World!
Chapter 4. Publishing applications with .NET Core 3.1
.NET Core 3.1 applications can be published to use a shared system-wide version of .NET Core or to include .NET Core.
The following methods exist for publishing .NET Core 3.1 applications:
- Framework-dependent deployment (FDD) - The application uses a shared system-wide version of .NET.
When publishing an application for RHEL, Red Hat recommends using FDD, because it ensures that the application is using an up-to-date version of .NET Core, built by Red Hat, that uses a set of native dependencies. These native libraries are part of the rh-dotnet31 Software Collection.
-
Self-contained deployment (SCD) - The application includes .NET. This method uses a runtime built by Microsoft. Running applications outside the
rh-dotnet31Software Collection may cause issues due to the unavailability of native libraries.
Prerequisites
Existing .NET Core application.
For more information on how to create a .NET Core application, see
4.1. Publishing .NET Core applications
The following procedure outlines how to publish a framework-dependent application.
Procedure
Publish the framework-dependent application:
$ dotnet publish my-app -f netcoreapp3.1 -c ReleaseReplace my-app with the name of the application you want to publish.
Optional: If the application is for RHEL only, trim out the dependencies needed for other platforms:
$ dotnet restore my-app -r rhel.7-x64 $ dotnet publish my-app -f netcoreapp3.1 -c Release -r rhel.7-x64 --self-contained false
Enable the Software Collection and pass the application name to run the application on a RHEL system:
$ scl enable rh-dotnet31 -- dotnet <app>.dll
You can add the
scl enable rh-dotnet31 — dotnet <app>.dllcommand to a script that is published with the application.Add the following script to your project and update the
APPvariable:#!/bin/bash APP=<app> SCL=rh-dotnet31 DIR="$(dirname "$(readlink -f "$0")")" scl enable $SCL -- "$DIR/$APP" "$@"
To include the script when publishing, add this ItemGroup to the
csprojfile:<ItemGroup> <None Update="<scriptname>" Condition="'$(RuntimeIdentifier)' == 'rhel.7-x64' and '$(SelfContained)' == 'false'" CopyToPublishDirectory="PreserveNewest" /> </ItemGroup>
Chapter 5. Running .NET Core 3.1 applications in containers
Use the dotnet/dotnet-31-runtime-rhel7 image to run a precompiled application inside a Linux container.
Prerequisites
Preconfigured containers.
The following example uses podman.
Procedure
Optional: If you are in another project’s directory and do not wish to create a nested project, return to the parent directory of the project:
$ cd ..
Create a new MVC project in a directory called
mvc_runtime_example:$ dotnet new mvc --output mvc_runtime_examplePublish the project:
$ dotnet publish mvc_runtime_example -f netcoreapp3.1 -c ReleaseCreate the
Dockerfile:$ cat > Dockerfile <<EOF FROM registry.redhat.io/dotnet/dotnet-31-runtime-rhel7 ADD bin/Release/netcoreapp3.1/publish/ . CMD ["dotnet", "mvc_runtime_example.dll"] EOF
Build your image:
$ podman build -t dotnet-31-runtime-example .
NoteIf you get an error containing the message
unable to retrieve auth token: invalid username/password, you need to provide credentials for theregistry.redhat.ioserver. Use the commandpodman login registry.redhat.ioto log in. Your credentials are typically the same as those used for the Red Hat Customer Portal.Run your image:
$ podman run -d -p8080:8080 dotnet-31-runtime-example
Verification steps
View the application running in the container:
$ xdg-open http://127.0.0.1:8080
Chapter 6. Using .NET Core 3.1 on OpenShift Container Platform
6.1. Installing .NET Core image streams
To install .NET Core image streams, use image stream definitions from s2i-dotnetcore with the OpenShift Client (oc) binary. Image streams can be installed from Linux, Mac, and Windows. A script enables you to install, update or remove the image streams.
You can define .NET Core image streams in the global openshift namespace or locally in a project namespace. Sufficient permissions are required to update the openshift namespace definitions.
Obtaining the RHEL 7 image streams requires authentication against the registry.redhat.io server using subscription credentials. These credentials are configured by adding a pull secret to the OpenShift namespace.
6.1.1. Installing image streams using OpenShift Client
You can use OpenShift Client (oc) to install .NET Core image streams.
Prerequisites
- An existing pull secret must be present in the namespace. If no pull secret is present in the namespace. Add one by following the instructions in the Red Hat Container Registry Authentication guide.
Procedure
List the available .NET Core image streams:
$ oc describe is dotnet
The output shows installed images. If no images are installed, the
Error from server (NotFound)message is displayed.Install the .NET Core image streams:
$ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json
When .NET Core image streams are already installed, you can include newer versions by running:
$ oc replace -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json
6.1.2. Installing image streams on Linux and macOS
You can use this script to install, upgrade, or remove the image streams on Linux and macOS.
Procedure
Download the script.
On Linux use:
$ wget https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh
On Mac use:
$ curl https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh -o install-imagestreams.sh
Make the script executable:
$ chmod +x install-imagestreams.sh
Log in to the OpenShift cluster:
$ oc login
Install image streams and add a pull secret for authentication against the
registry.redhat.io:./install-imagestreams.sh --os rhel7 [--user subscription_username --password subscription_password]
Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.
If the pull secret is already present, the
--userand--passwordarguments are ignored.
Additional information
-
./install-imagestreams.sh --help
6.1.3. Installing image streams on Windows
You can use this script to install, upgrade, or remove the image streams on Windows.
Procedure
Download the script.
Invoke-WebRequest https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.ps1 -UseBasicParsing -OutFile install-imagestreams.ps1
Log in to the OpenShift cluster:
$ oc login
Install image streams and add a pull secret for authentication against the
registry.redhat.io:./install-imagestreams.sh --OS rhel7 [-User subscription_username -Password subscription_password]
Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.
If the pull secret is already present, the
-Userand-Passwordarguments are ignored.
The PowerShell ExecutionPolicy may prohibit executing this script. To relax the policy, run Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force.
Additional information
-
Get-Help .\install-imagestreams.ps1
6.2. Deploying applications from source using oc
The following example demonstrates how to deploy the example-app application using oc, which is in the app folder on the dotnetcore-3.1 branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository:
Procedure
Create a new OpenShift project:
$ oc new-project sample-projectAdd the ASP.NET Core application:
$ oc new-app --name=example-app 'dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-3.1' --build-env DOTNET_STARTUP_PROJECT=appTrack the progress of the build:
$ oc logs -f bc/example-appView the deployed application once the build is finished:
$ oc logs -f dc/example-appThe application is now accessible within the project.
Optional: Make the project accessible externally:
$ oc expose svc/example-appObtain the shareable URL:
$ oc get routes
6.3. Deploying applications from binary artifacts using oc
You can use .NET Core Source-to-Image (S2I) builder image to build applications using binary artifacts that you provide.
Prerequisites
Published application.
For more information, see
Procedure
Create a new binary build:
$ oc new-build --name=my-web-app dotnet:3.1 --binary=trueStart the build and specify the path to the binary artifacts on your local machine:
$ oc start-build my-web-app --from-dir=bin/Release/netcoreapp3.1/publish
Create a new application:
$ oc new-app my-web-app
6.4. Using Jenkins slave
The OpenShift Container Platform Jenkins image provides auto-discovery of the .NET Core 3.1 slave image (dotnet-31).
For auto-discovery to work, you need to add a Jenkins slave ConfigMap yaml file to the project.
Procedure
Change to the project where Jenkins is (or will be) deployed:
$ oc project _project-name_
Create a
dotnet-jenkins-slave.yamlfile:NoteThe value used for the <serviceAccount> element is the account used by the Jenkins slave. If no value is specified, the
defaultservice account is used.kind: ConfigMap apiVersion: v1 metadata: name: dotnet-jenkins-slave-31 labels: role: jenkins-slave data: dotnet31: |- <org.csanchez.jenkins.plugins.kubernetes.PodTemplate> <inheritFrom></inheritFrom> <name>dotnet-31</name> <instanceCap>2247483647</instanceCap> <idleMinutes>0</idleMinutes> <label>dotnet-31</label> <serviceAccount>jenkins</serviceAccount> <nodeSelector></nodeSelector> <volumes/> <containers> <org.csanchez.jenkins.plugins.kubernetes.ContainerTemplate> <name>jnlp</name> <image>registry.access.redhat.com/dotnet/dotnet-31-jenkins-slave-rhel7:latest</image> <privileged>false</privileged> <alwaysPullImage>true</alwaysPullImage> <workingDir>/tmp</workingDir> <command></command> <args>${computer.jnlpmac} ${computer.name}</args> <ttyEnabled>false</ttyEnabled> <resourceRequestCpu></resourceRequestCpu> <resourceRequestMemory></resourceRequestMemory> <resourceLimitCpu></resourceLimitCpu> <resourceLimitMemory></resourceLimitMemory> <envVars/> </org.csanchez.jenkins.plugins.kubernetes.ContainerTemplate> </containers> <envVars/> <annotations/> <imagePullSecrets/> <nodeProperties/> </org.csanchez.jenkins.plugins.kubernetes.PodTemplate>Import the configuration into the project:
$ oc create -f dotnet-jenkins-slave.yaml
The slave image can now be used.
Example
The following example shows a Jenkins pipeline added to OpenShift Container Platform. Note that when a Jenkins pipeline is added and no Jenkins master is running, OpenShift automatically deploys a master. See OpenShift Container Platform and Jenkins for additional information about deploying and configuring a Jenkins server instance.
In the example steps, the BuildConfig yaml file includes a simple Jenkins pipeline configured using the dotnet-31 Jenkins slave. There are three stages in the example BuildConfig yaml file:
- The sources are checked out.
- The application is published.
The image is assembled using a binary build.
See Section 6.3, “Deploying applications from binary artifacts using
oc” for additional information about binary builds.
Procedure
To configure the Jenkins master-slave pipeline:
Create the
buildconfig.yamlfile:kind: BuildConfig apiVersion: v1 metadata: name: dotnetapp-build spec: strategy: type: JenkinsPipeline jenkinsPipelineStrategy: jenkinsfile: |- node("dotnet-31") { stage('clone sources') { sh "git clone https://github.com/redhat-developer/s2i-dotnetcore-ex --branch dotnetcore-3.1 ." } stage('publish') { dir('app') { sh "dotnet publish -c Release" } } stage('create image') { dir('app') { sh 'oc new-build --name=dotnetapp dotnet:3.1 --binary=true || true' sh 'oc start-build dotnetapp --from-dir=bin/Release/{buildconfig-var}3.1/publish --follow' } } }Import the
BuildConfigfile to OpenShift:$ oc create -f buildconfig.yaml
- Open the OpenShift console.
Go to Builds → Pipelines.
The
dotnetapp-buildpipeline is available.Click Start Pipeline.
Mote that it may take a while for the build to start because the Jenkins image(s) need to be downloaded first.
During the build you can watch the different pipeline stages complete in the OpenShift console. You can also click View Log to see the pipeline stages complete in Jenkins.
When the Jenkins pipeline build is complete, go to Builds → Images.
The
dotnetappimage is built and available.
6.5. Environmental variables for .NET Core 3.1
The .NET Core images support several environment variables to control the build behavior of your .NET Core application. You can set these variables as part of the build configuration, or add them to the .s2i/environment file in the application source code repository.
| Variable Name | Description | Default |
|---|---|---|
| DOTNET_STARTUP_PROJECT |
Selects the project to run. This must be a project file (for example, |
|
| DOTNET_ASSEMBLY_NAME |
Selects the assembly to run. This must not include the |
The name of the |
| DOTNET_PUBLISH_READRYTORUN |
When set to |
|
| DOTNET_RESTORE_SOURCES |
Specifies the space-separated list of NuGet package sources used during the restore operation. This overrides all of the sources specified in the | |
| DOTNET_RESTORE_CONFIGFILE |
Specifies a | |
| DOTNET_TOOLS |
Specifies a list of .NET tools to install before building the app. It is possible to install a specific version by post pending the package name with | |
| DOTNET_NPM_TOOLS | Specifies a list of NPM packages to install before building the application. | |
| DOTNET_TEST_PROJECTS |
Specifies the list of test projects to test. This must be project files or folders containing a single project file. | |
| DOTNET_CONFIGURATION |
Runs the application in Debug or Release mode. This value should be either |
|
| DOTNET_VERBOSITY |
Specifies the verbosity of the | |
| HTTP_PROXY, HTTPS_PROXY | Configures the HTTP or HTTPS proxy used when building and running the application, respectively. | |
| DOTNET_RM_SRC |
When set to | |
| DOTNET_SSL_DIRS |
Specifies a list of folders or files with additional SSL certificates to trust. The certificates are trusted by each process that runs during the build and all processes that run in the image after the build (including the application that was built). The items can be absolute paths (starting with | |
| NPM_MIRROR | Uses a custom NPM registry mirror to download packages during the build process. | |
| ASPNETCORE_URLS |
This variable is set to | |
| DOTNET_RESTORE_DISABLE_PARALLEL |
When set to |
|
| DOTNET_INCREMENTAL |
When set to |
|
| DOTNET_PACK |
When set to |
6.6. Creating the MVC sample application
s2i-dotnetcore-ex is the default Model, View, Controller (MVC) template application for .NET Core.
This application is used as the example application by the .NET Core S2I image and can be created directly from the OpenShift UI using the Try Example link.
The application can also be created with the OpenShift client binary (oc).
Procedure
To create the sample application using oc:
Add the .NET Core application:
$ oc new-app dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-3.1 --context-dir=app
Make the application accessible externally:
$ oc expose service s2i-dotnetcore-ex
Obtain the sharable URL:
$ oc get route s2i-dotnetcore-ex
Additional resources
6.7. Creating the CRUD sample application
s2i-dotnetcore-persistent-ex is a simple Create, Read, Update, Delete (CRUD) .NET Core web application that stores data in a PostgreSQL database.
Procedure
To create the sample application using oc:
Add the database:
$ oc new-app postgresql-ephemeral
Add the .NET Core application:
$ oc new-app dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-persistent-ex#dotnetcore-3.1 --context-dir app
Add environment variables from the
postgresqlsecret and database service name environment variable:$ oc set env dc/s2i-dotnetcore-persistent-ex --from=secret/postgresql -e database-service=postgresql
Make the application accessible externally:
$ oc expose service s2i-dotnetcore-persistent-ex
Obtain the sharable URL:
$ oc get route s2i-dotnetcore-persistent-ex
Additional resources
Chapter 7. Migration from previous versions of .NET
7.1. Migration from previous versions of .NET
Microsoft provides instructions for migrating from most previous versions of .NET Core.
When migrating from ASP.NET Core 2.0 to .NET Core 2.1, the following property should no longer be specified.
<PublishWithAspNetCoreTargetManifest>false</PublishWithAspNetCoreTargetManifest>
It should remain the default value for .NET Core 2.1. Make sure to remove this property from the project file and command line, if it is being specified there.
If you are using a version of .NET that is no longer supported or want to migrate to a newer .NET version to expand functionality, see the following articles:
- Migrate from ASP.NET Core 3.1 to 5.0
- Migrate from ASP.NET Core 3.0 to 3.1
- Migrate from ASP.NET Core 2.2 to 3.0
- Migrate from ASP.NET Core 2.1 to 2.2
- Migrate from .NET Core 2.0 to 2.1
- Migrate from ASP.NET to ASP.NET Core
- Migrating .NET Core projects from project.json
- Migrate from project.json to .csproj format
If migrating from .NET Core 1.x to 2.0, see the first few related sections in Migrate from ASP.NET Core 1.x to 2.0. These sections provide guidance that is appropriate for a .NET Core 1.x to 2.0 migration path.
7.2. Porting from .NET Framework
Refer to the following Microsoft articles when migrating from .NET Framework:
- For general guidelines, see Porting to .NET Core from .NET Framework.
- For porting libraries, see Porting to .NET Core - Libraries.
- For migrating to ASP.NET Core, see Migrating to ASP.NET Core.
Several technologies and APIs present in the .NET Framework are not available in .NET Core and .NET. If your application or library requires these APIs, consider finding alternatives or continue using the .NET Framework. .NET Core and .NET do not support the following technologies and APIs:
- Desktop applications, for example, Windows Forms and Windows Presentation Foundation (WPF)
- Windows Communication Foundation (WCF) servers (WCF clients are supported)
- .NET remoting
Additionally, several .NET APIs can only be used in Microsoft Windows environments. The following list shows examples of these Windows-specific APIs:
-
Microsoft.Win32.Registry -
System.AppDomains -
System.Drawing -
System.Security.Principal.Windows
Consider using the .NET Portability Analyzer to identify API gaps and potential replacements.
For example, enter the following command to find out how much of the API used by your .NET Framework application is supported by the newer version of .NET Core:
$ dotnet /path/to/ApiPort.dll analyze -f . -r html --target '.NET Framework,Version=<dotnet-framework-version>' --target '.NET Core,Version=<dotnet-version>'
Replace <dotnet-framework-version> with the .NET Framework version you are currently using. For example, 4.6. Replace <dotnet-version> with the version of .NET Core you plan to migrate to. For example, 3.1.
Several APIs that are not supported in the default version of .NET Core may be available from the Microsoft.Windows.Compatibility NuGet package. Be careful when using this NuGet package. Some of the APIs provided (such as Microsoft.Win32.Registry) only work on Windows, making your application incompatible with Red Hat Enterprise Linux.